1. Field of the Invention
This invention relates to parallel DC-DC converters and, in particular, to the distribution of a load evenly among the parallel converters.
2. Description of the Prior Art
When a power supply system comprising a plurality of DC-DC converters, connected in parallel, supplies power to a load, some of the converters carry less of the load than others. Such an uneven load distribution among the converters, particularly under light load conditions, creates noise which interferes with the fidelity of transmission of intelligence in telecommunications and is therefore unacceptable. Furthermore, the efficiency of the system is decreased because of uneven load distribution.
Many solutions have been proposed to insure uniform load distribution among converters. One solution calls for sensing the output current by locating a sensing device in the secondary or output circuit of each converter. A resistor, usually, is inserted in the secondary circuit, directly or indirectly, to develop a feedback signal. The feedback signal is compared with an average of all feedback signals to develop an error signal which is used to vary the pulse width of the signal which drives the switching transistor in that converter. While this method of sensing is desirable for low current output applications, the efficiency of the converter system drops in applications where the output current is high.